<?php
/*=======================================================================
 // File:        JPGRAPH_MESHINTERPOLATE.INC.PHP
 // Description: Utility class to do mesh linear interpolation of a matrix
 // Created:     2009-03-09
 // Ver:         $Id: jpgraph_meshinterpolate.inc.php 1709 2009-07-30 08:00:08Z ljp $
 //
 // Copyright (c) Asial Corporation. All rights reserved.
 //========================================================================
 */

/**
 * Utility function to do linear mesh interpolation
 * @param $aDat Matrix to interpolate
 * @param $aFactor Interpolation factor
 */
function doMeshInterpolate( &$aData, $aFactor ) {
	$m = new MeshInterpolate();
	$aData = $m->Linear($aData,$aFactor);
}

/**
 * Utility class to interpolate a given data matrix
 *
 */
class MeshInterpolate {
	private $data = array();

	/**
	 * Calculate the mid points of the given rectangle which has its top left
	 * corner at $row,$col. The $aFactordecides how many spliots should be done.
	 * i.e. how many more divisions should be done recursively
	 *
	 * @param $row Top left corner of square to work with
	 * @param $col Top left corner of square to work with
	 * $param $aFactor In how many subsquare should we split this square. A value of 1 indicates that no action
	 */
	function IntSquare( $aRow, $aCol, $aFactor ) {
		if ( $aFactor <= 1 )
		return;

		$step = pow( 2, $aFactor-1 );

		$v0 = $this->data[$aRow][$aCol];
		$v1 = $this->data[$aRow][$aCol + $step];
		$v2 = $this->data[$aRow + $step][$aCol];
		$v3 = $this->data[$aRow + $step][$aCol + $step];

		$this->data[$aRow][$aCol + $step / 2] = ( $v0 + $v1 ) / 2;
		$this->data[$aRow + $step / 2][$aCol] = ( $v0 + $v2 ) / 2;
		$this->data[$aRow + $step][$aCol + $step / 2] = ( $v2 + $v3 ) / 2;
		$this->data[$aRow + $step / 2][$aCol + $step] = ( $v1 + $v3 ) / 2;
		$this->data[$aRow + $step / 2][$aCol + $step / 2] = ( $v0 + $v1 + $v2 + $v3 ) / 4;

		$this->IntSquare( $aRow, $aCol, $aFactor-1 );
		$this->IntSquare( $aRow, $aCol + $step / 2, $aFactor-1 );
		$this->IntSquare( $aRow + $step / 2, $aCol, $aFactor-1 );
		$this->IntSquare( $aRow + $step / 2, $aCol + $step / 2, $aFactor-1 );
	}

	/**
	 * Interpolate values in a matrice so that the total number of data points
	 * in vert and horizontal axis are $aIntNbr more. For example $aIntNbr=2 will
	 * make the data matrice have tiwce as many vertical and horizontal dta points.
	 *
	 * Note: This will blow up the matrcide in memory size in the order of $aInNbr^2
	 *
	 * @param  $ &$aData The original data matricde
	 * @param  $aInNbr Interpolation factor
	 * @return the interpolated matrice
	 */
	function Linear( &$aData, $aIntFactor ) {
		$step = pow( 2, $aIntFactor-1 );

		$orig_cols = count( $aData[0] );
		$orig_rows = count( $aData );
		// Number of new columns/rows
		// N = (a-1) * 2^(f-1) + 1
		$p = pow( 2, $aIntFactor-1 );
		$new_cols = $p * ( $orig_cols - 1 ) + 1;
		$new_rows = $p * ( $orig_rows - 1 ) + 1;

		$this->data = array_fill( 0, $new_rows, array_fill( 0, $new_cols, 0 ) );
		// Initialize the new matrix with the values that we know
		for ( $i = 0; $i < $new_rows; $i++ ) {
			for ( $j = 0; $j < $new_cols; $j++ ) {
				$v = 0 ;
				if ( ( $i % $step == 0 ) && ( $j % $step == 0 ) ) {
					$v = $aData[$i / $step][$j / $step];
				}
				$this->data[$i][$j] = $v;
			}
		}

		for ( $i = 0; $i < $new_rows-1; $i += $step ) {
			for ( $j = 0; $j < $new_cols-1; $j += $step ) {
				$this->IntSquare( $i, $j, $aIntFactor );
			}
		}

		return $this->data;
	}
}

?>
